Institute for Preservation and Conservation of Chinese Ancient Books, Fudan University Library, Fudan University, 220 Handan Road, Shanghai 200433, China.
Shanghai Institute of Quality Inspection and Technical Research, 381 Cang Wu Road, Shanghai 200233, China.
ACS Appl Mater Interfaces. 2024 Mar 13;16(10):13091-13102. doi: 10.1021/acsami.3c19050. Epub 2024 Feb 29.
Paper-based cultural relics experience irreversible aging and deterioration during long-term preservation. The most common process of paper degradation is the acid-catalyzed hydrolysis of cellulose. Nowadays, deacidification has been considered as a practical way to protect acidified literature; however, two important criteria of minimal intervention and reversibility should be considered. Inspired by the superior properties of bacterial cellulose (BC) and its structural similarity to paper, herein, the mineralized BC membranes are applied to deacidification and conservation of paper-based materials for the first time. Based on the enzyme-induced mineralization process, the homogeneous and high-loaded calcifications of hydroxyapatite (HAP) and calcium carbonate (CaCO) nanoparticles onto the nanofibers of BC networks have been achieved, respectively. The size, morphology, structure of minerals, as well as the alkalinity and alkali reserve of BC membranes are well controlled by regulating enzyme concentration and mineralization time. Compared with HAP/CaCO-immersed method, HAP/CaCO-BC membranes show more efficient and sustained deacidification performance on paper. The weak alkalinity of mineralized BC membranes avoids the negative effect of alkali on paper, and the high alkali reserve implies a good sustained-release effect of alkali to neutralize the future generated acid. The multiscale nanochannels of the BC membrane provide ion exchange and acid/alkali neutralization channels between paper and the BC membrane, and the final pH of protected paper can be well stabilized in a certain range. Most importantly, this BC-deacidified method is reversible since the BC membrane can be removed without causing any damage to paper and the original structure and fiber morphology of paper are well preserved. In addition, the mineralized BC membrane provides excellent flame-retardant performance on paper thanks to its unique organic-inorganic composite structure. All of these advantages of the mineralized BC membrane indicate its potential use as an effective protection material for the reversible deacidification and preventive conservation of paper-based cultural relics.
纸质文物在长期保存过程中会经历不可逆转的老化和劣化。纸张降解最常见的过程是纤维素的酸催化水解。如今，脱酸已被认为是保护酸化文献的一种实用方法；然而，最小干预和可逆性这两个重要标准应该被考虑。受细菌纤维素 (BC) 优异性能及其与纸张结构相似性的启发，本文首次将矿化 BC 膜应用于纸张材料的脱酸和保护。基于酶诱导的矿化过程，分别实现了均匀且高负载的纳米羟基磷灰石 (HAP) 和碳酸钙 (CaCO) 纳米颗粒在 BC 网络纳米纤维上的矿化。通过调节酶浓度和矿化时间，可以很好地控制 BC 膜的矿物质尺寸、形态、结构以及碱度和碱储备。与 HAP/CaCO 浸泡法相比，HAP/CaCO-BC 膜在纸张上表现出更高效和持续的脱酸性能。矿化 BC 膜的弱碱性避免了碱对纸张的负面影响，而高碱储备意味着碱的良好持续释放效果，可中和未来产生的酸。BC 膜的多尺度纳米通道为纸张和 BC 膜之间提供了离子交换和酸碱中和通道，保护后纸张的最终 pH 值可以在一定范围内得到很好的稳定。最重要的是，这种 BC 脱酸方法是可逆的，因为 BC 膜可以被去除，而不会对纸张造成任何损坏，并且纸张的原始结构和纤维形态得到了很好的保留。此外，由于其独特的有机-无机复合结构，矿化 BC 膜为纸张提供了优异的阻燃性能。矿化 BC 膜的所有这些优点表明，它有望作为一种有效的保护材料，用于纸张文物的可逆脱酸和预防性保护。
